Phase 4 Stage 3: payment shell (multi-screen flow)

Six new screens under /payment/* + a paymentDraftProvider holding
mode/durationId/durationMinutes/priceIDR/paymentId/isFirstSessionDiscount
across the flow. PaymentEntryScreen handles the routing decision
(eligible+enabled -> /payment/discount-paywall, else /payment/method-pick)
and clears the draft on fresh entry.

Screens:
- discount_paywall_screen: S6 first-session discount with struck-through
  gimmick price + actual price + 'mulai · Rp{actual}' CTA -> /payment/method
- method_pick_screen: chat vs call cards
- duration_pick_screen: tier list with chat|call mode toggle that resets
  the selection on swap
- payment_method_screen: QRIS-first list, posts to existing
  /api/client/payment-sessions with mode/duration/price/discount/method
- waiting_payment_screen: qr_flutter QR (encodes paymentId in mock mode),
  20-min countdown header, 3s polling for status, pauses on background
  via WidgetsBindingObserver
- payment_expired_screen: retry CTA -> /payment/method with draft retained

Status mapping: real payment_sessions.status uses 'confirmed'/'consumed'
for paid (not 'paid' as in plan) and 'expired'/'abandoned' as terminal.

home_screen 'Mulai Curhat' CTA now pushes /payment/entry.

Dev-only /internal/_test/force-expire-payment endpoint to drive Maestro
flow 04_payment_expired.yaml without waiting 20 minutes. Gated behind
NODE_ENV !== 'production'.

chat_opening_provider PricingData extended to carry Phase 4 chat/call
groups + firstSessionDiscount, back-compat with the Phase 3 shape.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

client_app/lib/features/home/home_screen.dart

@@ -4,7 +4,6 @@ import 'package:go_router/go_router.dart';
 import '../../core/auth/auth_notifier.dart';
 import '../../core/availability/mitra_availability_notifier.dart';
 import '../../core/chat/active_session_notifier.dart';
-import '../chat/widgets/topic_selection_bottom_sheet.dart';
 
 /// Home screen.
 ///
@@ -53,10 +52,17 @@ class _HomeScreenState extends ConsumerState<HomeScreen> with WidgetsBindingObse
     }
   }
 
-  Future<void> _onStartChatPressed(BuildContext context) async {
-    final topic = await TopicSelectionBottomSheet.show(context);
-    if (topic == null || !context.mounted) return;
-    context.push('/payment', extra: {'topicSensitivity': topic});
+  void _onStartChatPressed(BuildContext context) {
+    // Phase 4 Stage 2 removes the home-screen topic sensitivity prompt; the
+    // ESP picks collected during onboarding feed the same column server-side
+    // (info-only — no longer drives matching). Mitras still flip
+    // `topic_sensitivity` mid-session via the AppBar toggle.
+    //
+    // Phase 4 Stage 3: enter the new multi-screen payment shell. The entry
+    // route picks discount-paywall vs. method-pick based on first-session
+    // eligibility. The legacy `/payment` route is preserved for the
+    // chat-history "Curhat lagi" path until Stage 5 migrates it.
+    context.push('/payment/entry');
   }
 
   @override